In one embodiment, a computing device receives an indication of a first user action by a first user. The computing device determines a topic of the first user action based on analyzing content associated with the first user action, and determines whether the first user has a preference to exclude posts associated with the topic or a category associated with the topic. If the first user has not indicated any preference to exclude posts associated with the topic or the category, then the computing device identifies a second user action by a second user and related to the topic, and determines whether the first user has indicated a preference to exclude posts associated with the second user. If the first user has not indicated any preference to exclude posts associated with the second user, a reference associated with the second user action is sent to the first user.